It seems like with the new update for Acrobat, by default all files open as tabs in a single Acrobat window, which is why Windows 11 is only showing 1 icon in the taskbar. I am unable to find where to change the default so PDFs all open in individual windows. The files can manually be dragged apart, but there's got to be a setting to just have them open in new windows by default. (If you manually separate the PDF tabs into separate windows, each PDF shows up in the task bar as a unique file.)